1. Field of the Invention
The present invention relates to an information recording apparatus using an exposure beam such as an electron beam, and particularly, to an information recording apparatus and an information recording method using a manufacture apparatus for manufacturing master disks of recording media having tracks, such as optical disks exclusive to reproduction, magneto-optical disks, or phase change type optical disks. The present invention further relates to a recording medium such as an optical disk reproduced from the master disk.
2. Description of the Related Art
Data-recordable optical recording media includes optical disks such a write-once type DVD-R (Digital Versatile Disc-Recordable), and a rewritable type DVD-RW (Digital Versatile Disc-Rewritable). In these optical disks, generally, rotation control information such as a wobbling signal used for the rotation control of an optical disk is previously recorded on tracks constituted of concave or convex portions, i.e., groove tracks or land tracks, when a master disk is produced, as well as a signal such as address information required for position searching in data recording on pre-pits.
For obtaining those optical disks, firstly predetermined concave and convex patterns are formed on a master disk along tracks corresponding to signals, and a disk stamper is formed from the recorded master disk. Then, using the stamper, a light-transmitting substrate and the like are formed by heating press work of a synthetic resin or the like or by injection-molding method, followed by the application of metallic deposition to the recorded surface having the patterns transferred thereon. The recording of the patterns to the master disk has been performed by the following method using an information recording apparatus. While rotating the recording surface, by appropriately feeding a header emitting a laser light beam in the radial direction thereof, a control has been performed such that the irradiating spot of the laser light beam creates track locus that have a spiral form or a concentric circular form at a substantially equidistant pitch. During the formation of the locus of the irradiating spot, the on and off switching of the laser beam is executed according to the rotational speed and the information contents to be recorded, so that the grooves and pre-pits for the information have been recorded on the master desk.
In recent years, research and development of a high-density recording medium excelling DVD in the density is proceeding to meet demand for the miniaturization of pitch in such tracks.
However, in the conventional track cutting of a master disk using a laser beam, that is, mastering, the recording resolution of the spot diameter of the laser beam for recording is limited by the wavelength of the laser beam and the numeral aperture NA of an objective lens.
Accordingly, there is a development and research for a master disk cutting method using exposure to an electron beam having a spot diameter smaller than that of the laser light beam because of an improvement in the recording resolution. For example, Japanese Patent Application kokai No. Hei 11-283283 discloses a method wherein, when forming latent images by electronic exposure of a resist layer with which a master disk is coated, the electron beam is alternately deflected and oscillated over a plurality of tracks, and the electron beam is modulated in its intensity so as to be made incident to the resist layer only at the positions to be exposed in a pulsating manner on respective tracks, whereby latent images are simultaneously formed over the plurality of tracks.
Such a conventional method requires the increase of deflection speed for pulses of emitted electron beam and a narrow convergence for a minute electron beam spot. This requirement raises a problem that the electron beam is not absorbed by the resist layer but passes therethrough, so that the exposure amount for each pulse is decreased, resulting in a reduced resolution. Also, in the conventional method, another problem has occurred that, since discrete latent images caused by the electron beam pulses are connected to one another, side surfaces of grooves or the like after a master disk has been developed cannot be smoothly formed. Additionally, the recording using the single oscillated electron beam in the conventional method has a drawback such that it is impossible to form latent image lines which are mutually different in the thickness for the pre-pits and grooves carrying mutually different information.
Moreover, Japanese Patent 3040887 (Patent Application kokai No. Hei 6-131706) discloses an electron beam exposure device wherein, so as to form latent images concentrically circular track patterns, the electron beam exposure process is preformed to the resist layer in such a manner that a stationary electron beam is irradiated to the recording surface of the rotating master disk for one rotation thereof and then, the master disk is shifted by one track pitch and stopped and then the stationary electron beam is irradiated to the recording surface of the rotating master disk for one rotation thereof again, and the master disk is shifted by one track pitch and stopped, and these operations are periodically repeated.
Such a conventional electron beam exposure device produces a drawback of time loss for stabilizing the rotation of the master disk at a predetermined position for starting the exposure because there is a rapid deceleration of the master disk in the stop period between traveling periods thereof. Further since the conventional electron beam exposure device requires a high precision of the master disk's position for electron beam exposure, it is difficult to produce concentrically circular track patterns with a high accuracy.